[PATCH 3.12 63/83] md/raid5: Use conf->device_lock protect changing of multi-thread resources.

From: Greg Kroah-Hartman
Date: Fri Dec 06 2013 - 17:27:40 EST

3.12-stable review patch. If anyone has any objections, please let me know.

------------------

From: majianpeng <majianpeng@xxxxxxxxx>

commit 60aaf933854511630e16be4efe0f96485e132de4 upstream.
and commit 0c775d5208284700de423e6746259da54a42e1f5

When we change group_thread_cnt from sysfs entry, it can OOPS.

The kernel messages are:
[ 135.299021] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 135.299073] IP: [<ffffffff815188ab>] handle_active_stripes+0x32b/0x440
[ 135.299107] PGD 0
[ 135.299122] Oops: 0000 [#1] SMP
[ 135.299144] Modules linked in: netconsole e1000e ptp pps_core
[ 135.299188] CPU: 3 PID: 2225 Comm: md0_raid5 Not tainted 3.12.0+ #24
[ 135.299214] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS 080015 11/09/2011
[ 135.299255] task: ffff8800b9638f80 ti: ffff8800b77a4000 task.ti: ffff8800b77a4000
[ 135.299283] RIP: 0010:[<ffffffff815188ab>] [<ffffffff815188ab>] handle_active_stripes+0x32b/0x440
[ 135.299323] RSP: 0018:ffff8800b77a5c48 EFLAGS: 00010002
[ 135.299344] RAX: ffff880037bb5c70 RBX: 0000000000000000 RCX: 0000000000000008
[ 135.299371] RDX: ffff880037bb5cb8 RSI: 0000000000000001 RDI: ffff880037bb5c00
[ 135.299398] RBP: ffff8800b77a5d08 R08: 0000000000000001 R09: 0000000000000000
[ 135.299425] R10: ffff8800b77a5c98 R11: 00000000ffffffff R12: ffff880037bb5c00
[ 135.299452] R13: 0000000000000000 R14: 0000000000000000 R15: ffff880037bb5c70
[ 135.299479] FS: 0000000000000000(0000) GS:ffff88013fd80000(0000) knlGS:0000000000000000
[ 135.299510] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 135.299532] CR2: 0000000000000000 CR3: 0000000001c0b000 CR4: 00000000000407e0
[ 135.299559] Stack:
[ 135.299570] ffff8800b77a5c88 ffffffff8107383e ffff8800b77a5c88 ffff880037a64300
[ 135.299611] 000000000000ec08 ffff880037bb5cb8 ffff8800b77a5c98 ffffffffffffffd8
[ 135.299654] 000000000000ec08 ffff880037bb5c60 ffff8800b77a5c98 ffff8800b77a5c98
[ 135.299696] Call Trace:
[ 135.299711] [<ffffffff8107383e>] ? __wake_up+0x4e/0x70
[ 135.299733] [<ffffffff81518f88>] raid5d+0x4c8/0x680
[ 135.299756] [<ffffffff817174ed>] ? schedule_timeout+0x15d/0x1f0
[ 135.299781] [<ffffffff81524c9f>] md_thread+0x11f/0x170
[ 135.299804] [<ffffffff81069cd0>] ? wake_up_bit+0x40/0x40
[ 135.299826] [<ffffffff81524b80>] ? md_rdev_init+0x110/0x110
[ 135.299850] [<ffffffff81069656>] kthread+0xc6/0xd0
[ 135.299871] [<ffffffff81069590>] ? kthread_freezable_should_stop+0x70/0x70
[ 135.299899] [<ffffffff81722ffc>] ret_from_fork+0x7c/0xb0
[ 135.299923] [<ffffffff81069590>] ? kthread_freezable_should_stop+0x70/0x70
[ 135.299951] Code: ff ff ff 0f 84 d7 fe ff ff e9 5c fe ff ff 66 90 41 8b b4 24 d8 01 00 00 45 31 ed 85 f6 0f 8e 7b fd ff ff 49 8b 9c 24 d0 01 00 00 <48> 3b 1b 49 89 dd 0f 85 67 fd ff ff 48 8d 43 28 31 d2 eb 17 90
[ 135.300005] RIP [<ffffffff815188ab>] handle_active_stripes+0x32b/0x440
[ 135.300005] RSP <ffff8800b77a5c48>
[ 135.300005] CR2: 0000000000000000
[ 135.300005] ---[ end trace 504854e5bb7562ed ]---
[ 135.300005] Kernel panic - not syncing: Fatal exception

This is because raid5d() can be running when the multi-thread
resources are changed via system. We see need to provide locking.

mddev->device_lock is suitable, but we cannot simple call
alloc_thread_groups under this lock as we cannot allocate memory
while holding a spinlock.
So change alloc_thread_groups() to allocate and return the data
structures, then raid5_store_group_thread_cnt() can take the lock
while updating the pointers to the data structures.

This fixes a bug introduced in 3.12 and so is suitable for the 3.12.x
stable series.

Fixes: b721420e8719131896b009b11edbbd27
Signed-off-by: Jianpeng Ma <majianpeng@xxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Reviewed-by: Shaohua Li <shli@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/md/raid5.c | 63 ++++++++++++++++++++++++++++++++---------------------
1 file changed, 39 insertions(+), 24 deletions(-)

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5214,15 +5214,18 @@ raid5_show_group_thread_cnt(struct mddev
return 0;
}

-static int alloc_thread_groups(struct r5conf *conf, int cnt);
+static int alloc_thread_groups(struct r5conf *conf, int cnt,
+ int *group_cnt,
+ int *worker_cnt_per_group,
+ struct r5worker_group **worker_groups);
static ssize_t
raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
{
struct r5conf *conf = mddev->private;
unsigned long new;
int err;
- struct r5worker_group *old_groups;
- int old_group_cnt;
+ struct r5worker_group *new_groups, *old_groups;
+ int group_cnt, worker_cnt_per_group;

if (len >= PAGE_SIZE)
return -EINVAL;
@@ -5238,17 +5241,19 @@ raid5_store_group_thread_cnt(struct mdde
mddev_suspend(mddev);

old_groups = conf->worker_groups;
- old_group_cnt = conf->worker_cnt_per_group;
-
if (old_groups)
flush_workqueue(raid5_wq);

- conf->worker_groups = NULL;
- err = alloc_thread_groups(conf, new);
- if (err) {
- conf->worker_groups = old_groups;
- conf->worker_cnt_per_group = old_group_cnt;
- } else {
+ err = alloc_thread_groups(conf, new,
+ &group_cnt, &worker_cnt_per_group,
+ &new_groups);
+ if (!err) {
+ spin_lock_irq(&conf->device_lock);
+ conf->group_cnt = group_cnt;
+ conf->worker_cnt_per_group = worker_cnt_per_group;
+ conf->worker_groups = new_groups;
+ spin_unlock_irq(&conf->device_lock);
+
if (old_groups)
kfree(old_groups[0].workers);
kfree(old_groups);
@@ -5278,33 +5283,36 @@ static struct attribute_group raid5_attr
.attrs = raid5_attrs,
};

-static int alloc_thread_groups(struct r5conf *conf, int cnt)
+static int alloc_thread_groups(struct r5conf *conf, int cnt,
+ int *group_cnt,
+ int *worker_cnt_per_group,
+ struct r5worker_group **worker_groups)
{
int i, j;
ssize_t size;
struct r5worker *workers;

- conf->worker_cnt_per_group = cnt;
+ *worker_cnt_per_group = cnt;
if (cnt == 0) {
- conf->worker_groups = NULL;
+ *group_cnt = 0;
+ *worker_groups = NULL;
return 0;
}
- conf->group_cnt = num_possible_nodes();
+ *group_cnt = num_possible_nodes();
size = sizeof(struct r5worker) * cnt;
- workers = kzalloc(size * conf->group_cnt, GFP_NOIO);
- conf->worker_groups = kzalloc(sizeof(struct r5worker_group) *
- conf->group_cnt, GFP_NOIO);
- if (!conf->worker_groups || !workers) {
+ workers = kzalloc(size * *group_cnt, GFP_NOIO);
+ *worker_groups = kzalloc(sizeof(struct r5worker_group) *
+ *group_cnt, GFP_NOIO);
+ if (!*worker_groups || !workers) {
kfree(workers);
- kfree(conf->worker_groups);
- conf->worker_groups = NULL;
+ kfree(*worker_groups);
return -ENOMEM;
}

- for (i = 0; i < conf->group_cnt; i++) {
+ for (i = 0; i < *group_cnt; i++) {
struct r5worker_group *group;

- group = &conf->worker_groups[i];
+ group = &(*worker_groups)[i];
INIT_LIST_HEAD(&group->handle_list);
group->conf = conf;
group->workers = workers + i * cnt;
@@ -5462,6 +5470,8 @@ static struct r5conf *setup_conf(struct
struct md_rdev *rdev;
struct disk_info *disk;
char pers_name[6];
+ int group_cnt, worker_cnt_per_group;
+ struct r5worker_group *new_group;

if (mddev->new_level != 5
&& mddev->new_level != 4
@@ -5496,7 +5506,12 @@ static struct r5conf *setup_conf(struct
if (conf == NULL)
goto abort;
/* Don't enable multi-threading by default*/
- if (alloc_thread_groups(conf, 0))
+ if (!alloc_thread_groups(conf, 0, &group_cnt, &worker_cnt_per_group,
+ &new_group)) {
+ conf->group_cnt = group_cnt;
+ conf->worker_cnt_per_group = worker_cnt_per_group;
+ conf->worker_groups = new_group;
+ } else
goto abort;
spin_lock_init(&conf->device_lock);
seqcount_init(&conf->gen_lock);


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